The thing that I see interesting here is the need to work backwards from the place the print will be and the intended viewing distance to the choice of lens and camera.

To get the rough theoretical "best" perspective (that 3-D walk into the photo or vertigo inducing look) for a given viewing distance of say 1 meter where the planned print size is 1 meter creates a 1:1 ratio of format:focal length (35mm film:35mm lens, 645 format:56mm lens, 6x7 format:70mm lens, etcetera...)

The "perfect" format to focal length ratio becomes basically a fixed value once the size and distance are known. This would be true of wall prints or billboards or wedding albums.

This is the perfect argument for using fixed length lenses that match the intended viewing distance to print size ratio. Zooming/cropping with your feet becomes imperative to maintaining the perfect ratio.

For me this also answers why the 85mm and 105mm lenses are so popular for portraits with 35mm cameras, it's the 8x10 prints that define the mass market. The short (un-cropped) edge 8" and the viewing distance of maybe 20" (roughly the distance hand held) = a 1:2.5 ratio. For 35mm multiply 35 by 2.5 and you get 87.5, for a hallway or desk setting, slightly longer than normal hand held distances you might get out to say a 105mm lens.

Following this logic out one more step, if I want to sell bigger prints than 8x10's, say 20" prints on the long edge, a shorter focal length would be better for a "normal" viewing distance.

For 35mm film, 35mm to 50mm lenses would theoretically create a "perfect" perspective for 16"x20" hallway prints or modern wedding album spreads (10"x20"). This same ratio pushes living room prints, with say a 5 foot planned viewing distance to have a long edge of about 42 to 60 inches.

I like that; shoot normal to wide, get closer with the camera, sell bigger and better prints!